In some methods for growing crystals, such as the Czochralski method, a seed crystal is brought into contact with the surface of a melt and then withdrawn from the melt. A crystal grows on the seed as it is withdrawn. The seed and growing crystal are sometimes also rotated about a vertical axis as they are withdrawn. Growth instabilities often occur in large crystals grown using this technique. As an example, the crystal may begin to grow in a spiral shape instead of a desired cylindrical shape. Growth instabilities may result in stresses due to variations in thermal expansion coefficients within the crystal, that may cause the crystal to shatter. Growth instabilities may be caused by accumulation of impurities in the melt, changes in the charge states of some of the melt constituents leading to creation of different molecular complexes, as well as by excesses of melt constituents accumulating at the interface between the surface of the melt and the growing crystal.